In recent years, in order to achieve high breakdown voltage and low loss of semiconductor devices, use thereof in a high temperature environment, and the like, silicon carbide has begun to be adopted as a material for semiconductor devices. Silicon carbide is a wide band gap semiconductor having a band gap larger than that of silicon, which has been conventionally widely used as a material for semiconductor devices. Hence, by adopting silicon carbide as a material for a semiconductor device, the semiconductor device can have a high breakdown voltage, reduced on-resistance, and the like. Further, the semiconductor device adopting silicon carbide as its material also has an advantage that its characteristics are less likely to be deteriorated when it is used in the high temperature environment, when compared with a semiconductor device adopting silicon as its material.
In the process for manufacturing a semiconductor device using silicon carbide as its material, impurities are introduced into a silicon carbide layer by ion implantation or the like, and thereafter activation annealing is performed. Thereby, desired carriers are generated in an impurity region within the silicon carbide layer. Since this activation annealing is performed at a high temperature exceeding 1500° C. for example, it is necessary to suppress surface roughness in the silicon carbide layer caused by heating. In response, processes for performing activation annealing with a carbon layer deposited on a surface of a silicon carbide layer have been proposed (see, for example, Japanese Patent Laying-Open No. 2001-68428 (PTD 1) and Japanese Patent Laying-Open No. 2013-26372 (PTD 2)).
PTD 1 discloses a process for performing activation annealing with a diamond like carbon (DLC) film or a film obtained by carbonizing a photoresist film being deposited on a surface of an epitaxial growth layer (a silicon carbide layer). Further, PTD 2 discloses a process for selectively removing silicon from a surface layer portion of a silicon carbide layer to form a carbon layer, and thereafter performing activation annealing.